yea ok. yes shadow king lived in a different dimesion the astral plains and proffesor X put him their and his powers are: exists as an entity of pure psychic energy, feeds off the negative emotions found in human souls with his telepathic powers, direct massive psionic energy into the physical plane to reform matter
amahl farouk is actually a decently interesting character, if you look into the ramifications of all of his actions. the first 'evil mutant' xavier came across, he was a factor in the decision to begin the X-Men. he also, as noted by jury, possessed karma, which had lasting effects on her personality. and his reappearance in X-Treme X-Men, what with the fight against psylocke and her subsequent loss of her telepathic abilities, he's had numerous lasting effects.
and, there are very few characters who would have sufficient strength to live on as an astral body after 'dying' at the hands of xavier. like him or not, he deserves some credit.
and it's astral PLANE. plain is a flat expanse of land, or an adjective meaning ordinary or without distinction. plane is a two dimensional non-physical concept, or, in spiritual terms, a varying state of living or place of inhabitance. to be alive on the 'astral plane' is to have transcended human existence and survive as a body of pure thought, or psionic, energy. making the transfer, and permanently, is a feat even the majority of the greatest telepaths still alive, in the marvel universe, would be unable to perform.